The present invention relates generally to the field of digital detection, and more particularly to single-flux-quantum (SFQ) digital detection devices.
Josephson junctions are known. A Josephson junction is made up of two superconductors coupled by a weak link. Several types of weak links are known, including insulators, non-superconducting metals, and physical constrictions. Josephson junctions have been used to construct Josephson comparators. In at least some Josephson comparators, a pair of Josephson junctions, operating on quantum mechanical principles, act together as a decision-making pair to signal whether or not an input current is above or below a threshold level whenever a clock pulse is applied. This threshold level is known to be subject to physical noise, which blurs the threshold level such that in practice it is actually a range, known as the “gray zone” of the comparator. Typical Josephson comparators have a noise-limited sensitivity, or difference required between signal levels for accurate detection, on the order of a few microamps. Properties of Josephson comparators can include extremely high speed operation, low power consumption, low noise, and high sensitivity, and as a result these comparators have found use in devices such as single-flux-quantum (SFQ) analog-to-digital converters (ADCs) and other applications where the value of such properties justifies the costs of their production and operation. Among the uses proposed for Josephson junctions has been as readout support for qubits in a quantum computing device.